The present invention relates to a fiber splicing device for splicing optical fibers to each other and to subassemblies used in a fiber splicing device.
When handling optical fibers intended for telecommunication in connection with splicing, movable holders, clamps or clips are used, which generally have the shape of low rectangular blocks including lids, which securely hold or clamp the fiber or fibers. Such a holder including an inserted fiber is placed in a more or less accurate way in the machine or device used, such as on movable blocks in a fiber splicing machine, see for example Swedish patent No. 9300578-3, publication No. SE 500915, which discloses a splicing device for splicing fiber ribbons using a parallelogram structure allowing a movement that is nearly but not perfectly linear. The deviation from a linear movement causes problems in those cases where a very accurate positioning of the fibers is required.
A fiber splicing device for splicing primarily ribbon fibers is disclosed in U.S. Pat. No. 5,961,865 and it includes e.g. electrodes placed and secured in an electrode housing, and fiber hold-down means to securely press the fiber ends into guiding V-grooves. The fiber hold-down means comprise a pressing assembly mounted at a pressing-down arm and having flat surfaces at bottom ends of elastically biased, movable pressing blocks. In the pressing-down movement said flat surfaces may not move perfectly perpendicular to the fibers, this causing the fibers to slightly move in the fiber longitudinal direction, resulting in splices that are not made in an optimum way and hence e.g. can have a too large optical loss. The disclosed splicing device also has light illuminating means emitting light hitting cameras, the light path from the illuminating means passing the splice position in a relatively large angle in relation to the common longitudinal axes of the electrodes, this giving the splicing device a large total height so that it cannot be easily handled, in particular when used in the field.
It is an object of the invention to provide a fiber splicing device having improved means for holding a fiber in a guiding or alignment groove.
It is another object of the invention to provide a fiber splicing device having means allowing an accurate linear movement of fiber holders.
It is another object of the invention to provide a fiber splicing device having electrodes which have points located at accurate positions in the relation to a splicing position.
It is another object of the invention to provide a fiber splicing device having a small total height.
It is another object of the invention to provide a fiber splicing device that can be easily handled.
A device for splicing optical fibers to each other comprises in the conventional way fiber retaining or holding means and some heating means for heating fibers at a splice position, such as electrodes between the points of which an electric arc is formed at the splice position, for fusion splicing the fibers to each other. Guiding grooves are used for aligning the ends of the fibers with each other. The guiding grooves can be formed in a surface of an alignment block. Hold-down means press and retain the fiber ends in the guiding grooves. In order not to give any longitudinal displacement of the fibers ends in the operation when the holding down-means are brought into contact with the fiber ends, the hold-down means include elastically biased, circular-cylindrical surfaces acting to press on the free, top surfaces of the fiber ends, the cylindrical surfaces being surfaces of elements that are mounted to rotate freely. The circular-cylindrical surfaces are preferably the outer surfaces of the outer races of roller bearings. The inner races of the bearings can be attached to an elastically biased hold-down assembly that is mounted to move in a holding arm. The holding arm can be mounted to swing or be folded down and up, to a swung-down position in which the hold-down means press on the fiber ends and a swung-up position in which the fiber ends are exposed and free. Some means such as a weight mounted to the holding arm can be used, arranged to firmly hold the holding arm in the swung-down position thereof.
The splicing device further can comprise a multiple parallelogram structure allowing very accurately linear displacements of at least one part thereof, such as of a fiber holding portion. The parallelogram structure includes at least two individual parallelograms, each having a free, stiff outer side. Their inner sides are formed by a common, stiff fiber holding portion. The fiber holding portion is attached to the free outer sides through lateral interior sides of the parallelograms. These lateral sides have the shape of thin plates and they are so thin that they can be elastically bent. This bending is performed in only one plane due to the fact that the lateral sides are of an elastic but still relatively stiff material such as a metal, typically aluminum or steel, to the flat strip-like shape of the sides and to their rigid attachment to or continuation into the relatively totally stiff outer and inner sides.
The parallelogram structure can further comprise at least one end portion and a center portion which are rigidly attached to a base of the device. The free outer sides of the parallelograms are then attached to the end portion and the center portion through lateral exterior sides having a shape substantially identical to that of the lateral interior sides and allowing a bending in only one plane. The interior and exterior lateral sides are then arranged in pairs so that the interior and exterior sides of such a pair extends at the sides of and in parallel to each other at a constant distance of each other.
The electrodes if used can as conventional have substantially smooth, cylindrical main portions continuing into electrode points. The electrodes may be provided with positioning rings. An electrode housing then has electrode grooves or recesses for mounting the electrodes. The positioning rings can include inner cutting edges penetrating into the surface material of the main portions and are located at a predetermined distance from the point of the respective electrode. The rings are received by positioning grooves in an electrode housing, the grooves having a width substantially agreeing with that of the rings, this giving the electrode points accurate, predetermined positions.
The splicing device can further comprise a hold-down base that is attached to the electrode housing and includes an upstanding portion. A light source may be mounted in the upstanding portion to illuminate the splicing position between the electrode points, the path of the illuminating light hitting the light sensitive surface of a camera having a relatively small angle in relation to the longitudinal axis of the electrodes. The hold-down base can also secure one of the electrodes in the electrode groove or recess provided therefor.
The relatively small angle of the illumination path can be at most 30xc2x0 in relation to the common axis of the electrodes or generally in the range of 15-30xc2x0 and preferably substantially 25xc2x0.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.